1. Technical Field
The present invention relates generally to automatic meter reading technology for remotely collecting data about various types of energy consumption (electricity, gas, water, heat, etc.) from individual customers using wired/wireless communication and, more particularly, to an advanced metering infrastructure system and advanced metering method using the system, which can guarantee the reliable transmission of meter data while utilizing existing wired or wireless communication methods, such as Power Line Communication (PLC), ZigBee, Binary Code Division Multiple Access (B-CDMA) or Wireless Fidelity (WiFi) communication which can be constructed at comparatively low cost and can be easily constructed using a self-organizing network.
2. Description of the Related Art
Generally, as scientific technology has been developed, the phenomenon in which tasks performed by human beings are automated or processed by machines has become commonplace. Among these tasks, automatic meter reading includes Automatic Metering Infrastructure (AMI) technology for automatically measuring the amount of water, electricity, gas, etc. consumed by individual homes or offices from a remote location without a meterman having to personally visit the home or office.
As shown in FIG. 1, a typical AMI system includes an electronic meter 300, a wired or wireless slave communication modem 310, a meter reading server 100, and a data concentrator 200. The electronic meter 300 (such as an electronic watt-hour meter, an electronic gas meter, an electronic water meter, etc.) measures/determines and stores various types of energy consumption. The slave communication modem 310 can be mounted inside or outside of the electronic meter 300. The meter reading server 100 manages meter data, automatically bills customers for corresponding energy consumption based on the meter data, and manages the customers at the center of the system. The data concentrator 200 is disposed between the meter reading server 100 and the electronic meter 300 and is configured to collect various types of energy consumed by each customer from the electronic meter 300 using wired or wireless communication, and transmit information about the collected energy consumption to the meter reading server 100.
Communication between the data concentrator 200 and the meter reading server 100 is performed either by using optical communication such as for a Hybrid Fiber Coaxial (HFC) network that guarantees high reliability, or by leasing and using the lines of 3G/4G communication companies. In contrast, narrowband or wideband wired communication such as Power Line Communication (PLC), and small-power wireless communication that uses an unlicensed frequency band such as ZigBee, Binary Code Division Multiple Access (B-CDMA) or Wireless Fidelity (WiFi), can be used as the wired or wireless communication means used between the data concentrator 200 and the electronic meter 300.
Since all of methods of carrying out the above-described wireless communication between the data concentrator 200 and the electronic meter 300 make use of an unlicensed frequency band (an Industrial, Scientific and Medical (ISM) band), only the maximum transmission power needs to be observed in the licensed frequency band without preliminary notice having to be given, and thus there is the advantage of a communication network being easily constructed at low cost. In contrast, it is disadvantageous in that due to variations in the external environment such as noise and disturbances, the reliability of communication cannot be guaranteed.
Representative international standard communication protocols used for an advanced metering infrastructure include IEC 62056 standard in Europe and Asia and ANSI C12 standards in North America. Both the IEC 60256 and ANSI C12 standards are based on a server-client structure. This denotes a structure in which a data concentrator (acting as a client), or a meter reading server (acting as a client) in the absence of a data concentrator, requests meter data, and in which an electronic meter (acting as a server) responds only to the request for meter data. The meter reading engines of data concentrators that are currently being operated in Korea are designed to periodically perform a meter reading process every 15 minutes, and sequentially read meter data from a maximum of 200 electronic meters in a polling manner during one 15 minute cycle. A premise of such a meter reading process is that the stability and reliability of communication between the client and the server are guaranteed. In this case, in order to communicate with electronic meters, the communication interface of a slave communication modem (PLC, B-CDMA, ZigBee or WiFi modem) mounted outside or inside of each electronic meter provides reliable communication in a wired manner, such as optical communication or RS-232/485 communication. However, methods used by communication between the slave communication modem and the master communication modem of a data concentrator typically installed on a telegraph pole are communication methods, such as PLC and WiFi, which are mainly based on shared media. Since these communication methods respectively use a power line and radio waves as communication media, they are sensitive to variations in the external environment, and are then vulnerable to a channel environment that is varying in real time, noise and interference. In addition, since those communication methods use Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol methods based on mutual competition in shared media, a temporary data transmission delay or an intermittent communication link failure inevitably results, and thus a problem arises in that stability and reliability are very unsatisfactory.
For example, the rates of success in the reading of pieces of load profile (LP) data collected from the watt-hour meters of 5 to 50 households during one 15 minute cycle according to the PLC method that is currently being used in Korea Electric Power Corporation (KEPCO) are shown in FIG. 2. The success rate of periodic meter reading indicates that if meter reading has succeeded only once among a plurality of meter reading trials within 24 hours, it is determined that successful meter reading is performed. This rate is 98.9% on the average for the whole country, but the success rate of LP meter reading is maintained merely at 56.9%. In particular, it can be seen that compared to periodic meter reading or current meter reading (with a data size of about 100 bytes), the success rate of LP meter reading is very low. The reason for this is that due to transmission errors caused by the instability of a link which may occur during the transmission of LP data having a size of several tens of Kbytes, and several retrials of meter reading caused by the occurrence of the transmission errors, a lot of time is wasted collecting meter data, and thus it is impossible to collect LP data from the watt-hour meters of other downstream customers during the period of 15 minutes. Furthermore, in the future, because Demand Response (DR) service is being promoted, it is expected that the time for which LP data is collected (the recording cycle) will become shorter, and thus a fundamental solution method for this is required.